How BIM is Creating Scope Overlap for the MEP Design Industry?

As the MEP (M&E) industry worldwide continues to turn to parametric 3D model-based building services design and coordination processes, the question of who does what between contractors and consultants has re-emerged. One of the challenges in the modern building services industry concerns the effective control of BIM models between MEP Consultants and MEP Contractors.

BIM has many benefits including: greater collaboration between stakeholders, improved design performance, less constructability issues on-site and cost efficiency. However, implementing BIM requires successfully managing scope definition and delivery as well as the information flow between the MEP (M&E) consultant, the MEP (M&E) contractor, several sub-contractors and shop fabricators. However, BIM can create scope overlap (and therefore costs and delays for the project) between MEP (M&E) consultants, contractors and other downstream participants.

In the traditional system, where 2D design data is received, the MEP contractor would be responsible for services coordination and clash detection. He/she would overlay the 2D drawings of each of the services (HVAC, electrical, and plumbing) and perform a detailed coordination exercise - usually by using 3D tools or by using BIM tools. The end result would be a model that is spatially coordinated that can then be used for installation drawing creation and subsequent fitting/installation.

The traditional approach (2D drawing deliverables) did not require design consultants to think about constructability and spatial coordination. However, the BIM process calls for MEP (M&E) BIM consultants to create clash-free 3D MEP models before creating 2D design drawings for contractors to use. As the consultant is also handing over their BIM model (which is increasingly clash free and coordinated to some extent) he/she is in effect carrying out some of the scope traditionally taken on by contractors. However and more importantly, the MEP model from the consultant is not always coordinated in the way that the services would be installed or be cost effective for an MEP contractor.

Though the consultants' BIM MEP model may be clash-free and spatially coordinated with the architectural and structural systems, the 3D model provided to the contractor by the consultant may fall short due to a number of reasons such as: i) procurement-led changes for materials and equipment; ii) it may not represent the actual installation process or layout; iii) the layouts may not be efficient i.e. allowing for too many bends and connections; iv) there may not be adequate allowance for lagging; v) there may not be adequate allowance for installation/hanging; and vi) there may not be allowance for access for maintenance purposes. In short, the consultant's 3D model may be spatially coordinated but not adequate for installation.

Without updating the BIM model to his own fitting and installation requirements/standards, the contractor will not experience constructability issues until in the field. At that stage it is almost too late to make too many changes and the installation will be compromised as a review of the model and revised drawings at that late stage will almost certainly create additional costs and fees.

This additional work by the contractor is in effect repeating the modelling exercise (as well as the drawing exercise) and is the key area of scope overlap and therefore additional time and cost which will impact project profitability and schedules.

To many observers, such an overlap defeats the purpose of employing MEP (M&E) BIM methods. With more time at the start of the process to define the deliverables of each party the scope can be reduced.

There are three alternatives available to the project team to avoid scope overlap in this manner. Firstly, the consultant may create a BIM model but may not focus on creating a coordinated or clash free model. He/she would use the model to then create design drawings. This would provide the contractor with a model that is not coordinated but with efficient routes and outlets for services that can then be fine-tuned. This approach would reduce BIM modelling time for the consultant as it removes the coordination 'headache'.

Secondly, he may create a 2D design as in the traditional non-BIM era. This will still allow BIM model creation by the contractor and therefore project’s need for BIM will still be served. This method allows the contractor to create a coordinated BIM model using specialist MEP coordination firms if needed.

The third approach is for the design consultants to employ specialist a MEP coordination firm that understands and possesses 'coordination for installation' skills. By employing these skills at the design stage the output is more likely to be more useful for the contractor whose role may then be to fine tune the model and then create drawings.

By managing MEP projects using one of these methods scope overlap will be reduced and projects will be more effectively managed and delivered during the pre-construction and BIM stages. The end result will be a gain for clients and a more positive and effective use of BIM technology to deliver MEP BIM projects.

Kuldeep Bwail, Director at XS CAD, providing 3D Architectural Modelling,3D BIM Modeling to Homebuilder, Architect